1. Field of the Invention
The present invention relates to a communications terminal apparatus, a reception apparatus, and a method for transmitting and receiving text data generated in a key operation.
2. Description of the Related Art
Conventionally, a technology of generating text data and converting Kana to Kanji by operating the keyboard of a personal computer, a mobile telephone, etc. has been studied (for example, refer to U.S. Pat. No. 5,818,437, JP11-312046A, JP54-139356A and JP58-144246A.
Furthermore, in recent years, in a communications terminal such as a mobile telephone, etc., a service of transmitting text data generated using an input interface such as a keyboard, etc. has become widely spread.
In the conventional technology, text data is represented by a standardized character code string. As a standardized character code string, for example, ASCII (American Standard Code for Information Interchange) is used in English, and Shift-JIS (Japanese Industrial Standards) is used in Japanese. Since a character code corresponds one to one to a character, it is necessary to define codes for the number of types of characters used. For example, English ASCII having a relatively smaller number of types of characters requires 8 bits to represent one character while Japanese Shift-JIS having a larger number of types of characters requires 16 bits. Generally, when text data is transmitted, a character code string configuring a plurality of character codes is transmitted. The amount of information is obtained by a product of the amount of information specific to character code (for example, 8 bits for ASCII) and the number of character codes. When a character code string is represented by a smaller amount of information, the communications cost can be reduced. Therefore, the band width which is the resources can be more efficiently used.
Since there are several text data compressing methods in which a given character code string is represented by a smaller number of codes, it is possible to reduce the text data transmission cost using these methods. For example, when a character is input by a user from an input interface such as a keyboard, etc., the communications terminal generates a character code string (text data to be transmitted), compresses the character code string in the text data compressing method such as the LZ77 (for example, refer to “A Universal Algorithm for Sequential Data Compression” IEEE Transactions on Information Theory 23 (3):337-343 (1977) by Jacob Ziv, Abraham Lempel; hereinafter referred to as Reference 1), the BSTW (for example, refer to “A locally adaptive data compression scheme” Communications of the ACM, 29:320-330, 1986 by J. Bentley, D. Sleator, R. Tarjan, and V. Wei; hereinafter referred to as Reference 2), etc., and then transmits the compressed data. Then, the receiving communications terminal restores the compressed data to the original character code string in the decompressing method corresponding to the compressing method, and displays the result on the output interface such as a display, etc. The compressing methods such as the LZ77, the BSTW, etc. are performed by using the bias of the distribution of the array of code string (frequency and position information about a specific array are defined as a feature amount), and replacing a part of the code string with a smaller number of codes.
However, since the above-mentioned conventional methods represent by codes not only the number of types of characters but also the pointer to the specific character code string and the position information, the amount of information specific to a code increases (since there are restrictions on the type of characters representable by the same bit, it is also possible not to increase the amount of information specific to a code) and sufficient compression efficiency cannot be attained. However, since the decrease of the number of codes compensates for the increase of the amount of information specific to codes, the methods can be practically used.
As described above, it is not possible to sufficiently reduce the amount of information about text data to be transmitted.